iio: light: cm3605: mark PM functions as __maybe_unused

When CONFIG_PM_SLEEP is disabled, we get a harmless warning

drivers/iio/light/cm3605.c:292:12: error: 'cm3605_pm_resume' defined but not used [-Werror=unused-function]
drivers/iio/light/cm3605.c:281:12: error: 'cm3605_pm_suspend' defined but not used [-Werror=unused-function]

Marking the functions as possibly unused avoids the warning without
needing to add an #ifdef.

Fixes: 8afa505c1230 ("iio: light: add driver for Capella CM3605")
Signed-off-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/light/cm3605.c

···
 	return 0;
 }
 
-static int cm3605_pm_suspend(struct device *dev)
+static int __maybe_unused cm3605_pm_suspend(struct device *dev)
 {
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 	struct cm3605 *cm3605 = iio_priv(indio_dev);
···
 	return 0;
 }
 
-static int cm3605_pm_resume(struct device *dev)
+static int __maybe_unused cm3605_pm_resume(struct device *dev)
 {
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 	struct cm3605 *cm3605 = iio_priv(indio_dev);